Multidisciplinary evidence for synchroneity between Ontong Java Nui volcanism and early Aptian oceanic anoxic event 1a.

The volcanic episodes forming Ontong Java Nui (OJN) likely caused late Barremian to mid-Aptian paleoenvironmental perturbations, the most substantial of which was early Aptian oceanic anoxic event (OAE) 1a (120 million years ago). However, recent estimates on younger OJN eruption ages cast doubt on the link between OJN volcanism and OAE1a. Here, we further demonstrate the synchroneity between OJN volcanism and OAE1a by refining the chronology of Pacific volcanogenic sedimentary records on Magellan Rise, nearby OJN, with detailed osmium and carbon isotopic stratigraphy. Our geochemical data reveal that a thick tuffaceous interval at this site was deposited during OAE1a. Furthermore, multisite compilation of osmium isotopes, Pacific volcanic ash beds, and paleontological data just above OJN basalts illustrate that explosive OJN eruptions spanned ~5 million years, peaking around OAE1a. Their synchroneity strongly indicates that OJN volcanism most likely caused OAE1a and relevant late Barremian to mid-Aptian environmental perturbations.